1. Field of the Invention
The invention relates to an automatic pupillometer with visual verification.
A pupillometer is an appliance designed to measure the pupillary distance of an individual. It consists in using a light source suitable for generating a corneal reflection on at least one of the eyes of the individual, and in proceeding to locate said reflection.
2. Description of the Related Art
Such a pupillometer may be manual, e.g. as described in patent document FR 1 506 352.
The appliance is then provided with three windows, two windows reproducing the eyeglass frame that is to be placed on the nose of the individual, and an opposite window where the eye of an observer responsible for the measurement is placed at the focus of a collimator lens enabling the light source to be positioned at infinity to correspond to the far vision of the individual. The lens may be movable in translation along the sighting axis, so as to enable a near vision measurement to be taken; the lens is then moved closer to the light source. The observer in the measurement position moves a movable marker and causes it to correspond with the corneal reflection so as to obtain the trace of the axis of each pupil and thus measure the pupillary half-distance for each eye of the individual.
That type of manual pupillometer takes time and raises problems with measurement accuracy.
More recently, automatic pupillometers have been proposed, e.g. as described in patent document FR 2 618 666.
The light rays corresponding to the corneal reflections therein are directed towards a detection receiver, which is a photosensitive receiver or a photodiode, and the pupillary distance is then calculated electronically. There is no need for an observer, with the measurement being performed completely automatically.
That type of pupillometer, which is particularly accurate since it is independent of an operator, nevertheless raises the following problems.
The individual whose pupillary distance is to be measured may behave in a way that impedes good measurement. For example, the individual may close the eyes, may blink, or may look in the wrong direction, i.e. away from the light source. This can lead to a wrong measurement of the pupillary half-distance, or indeed to a wrong measurement of the pupillary distance, if the individual is not looking at infinity. In addition, ambient lighting conditions may disturb the measurement, thereby giving rise to inaccurate values.
In an automatic pupillometer, it is presently not possible to detect such an error.
Logically, and given the way this technique of measurement by pupillometry is developing, it is possible to envisage verifying proper positioning of the eyes of an individual in a manner that is likewise automatic.
Nevertheless, it is not always easy to verify that the eyes are open, since it can happen for example that a corneal reflection is partially visible, with the photograph being taken at an instant when the eyelid is moving, thus leading to a result being obtained that is approximate in terms of accuracy, but that cannot be said to be wrong.
When verification is possible, it is necessary to envisage using electronic components that are capable of performing numerous calculations in order to analyze the image. Such components are generally quite expensive, bulky, and they consume large amounts of electrical energy, thus raising difficulties for an appliance that is portable.